Radiator



0. G. WENDEL Jan. 15, I935.

RADIATOR Filed Feb. 12, 1 934 4 Sheets-Sheet l III/I IN YEA 70f? ATTORNEYS Jan. 15, 1935. o. G. WENDEL 1,938,224

' I RADIATOR Filed Feb. 12, 1934 4 Sheets-Sheet 3 Jan. 15, 1935.

RADIATOR Filed Feb. 12, 1954 4 Sheets-Sheet 4 INVENTOI? OTTO G. WE/VDfL.

o. G. WENDEL 1,988,224

radiation be used with convection currents but preferably .usedzwith airi-deliveredmnder premurc as; by a tan and; guided by: a casing such asrmdicated at 1.1a. inthe accompanying: :drawings. .V 3. F115." .1 Whenthe sections are iconnectedztogether in series they are so. connected byza hexagoninipple designated l2. When so connectedwthe spacebetween the marginal; edges. adjacentthe. :fins of theadiaoent sections in the examplel have cited is; 1% inches. The:design,.however-, is not limited to-this dimension since; byusei 50f: longer. or shorter nipples this dimension canu'be varied.

.Jnv actual test of this-radiator 10f my-. -invention in comparison with thexbest radiatcr sections and the. most efiicient .knojwn intheart-of cast ironradiatorstoday, I secure the following results: .;when comparing the 'two, :radiators at; equal iriction, the radiator .of. myrinventionmweighs 10% of the old radiator, requires:63%"';of the space of the ;oldrradiator,and provides'zzlil9-% of til-1ev heating surface or the old iradiator. I further-findz that-two: sections :-or stacks: of .the

present radiator would do the worklot 2.4.sta'cks cfythe oldradiaton i ;When comparing the best. radiator of the old art'with my present invention ,onbthe basisof velocity of the:air;passingg thereover, I find. that my new radiatoriroi. =thisiinvention weighs 71% of; the o1d;radiator;.takes up '68% ofggthespace occupied :iby .the old radiator 1 and has 12&% of the heating; surface-of. the old' radiator. I Two.v stacks :01: the new. radiator do the work of $2.3. stacksfofthe oldradiator. The radiator of this invention requires.83% of :thefriction of theiold radiators} Furthermore-the new radiator stands a -maximum hydraulic pressure of. 1290 pounds gauge as compared withfthemaxn mum pressure of the old radiatorlof .1501 pounds. The new radiator is, therefore, 30,%..li'ghter. than the old radiator and occupies less space. it issuperior whether compared on .ithebasi's oi equal-friction or equal velocity. The. significance of these comparisons will, be. apparentlivhen' it is. understood thatone-of-the primary uses of this radiation is ,in :forced; blast systems where the space occupiedpthelweight.involved, .the re.- sistance to air flow and the rate of heattransfer' are such vital factors as tmconstitute .the difierence between failuregand' success-in the operation of aforced draft system. Theradiator' of my invention makes it. possible to use cast iron. with all of its advantagesin competition with radiators of otherfimaterials. -Whi1e I do not desire to confine myqinventionto cast iron, yet its advantagesibecom'e apparentxiwhen oast iron, is used as a. medium .ofaitsembodimentand the basiswofits comparison evenrwith other materialswin other designs. 1 ,While not int. nding :to limit .m .;.inve'ntion.to allor; a large part ;of.= the. .following features, nevertheless the following is a, summarys-ofvthe numerous 1 features of operation and. constructioninherent in;.the construction :and method oi -operation of the apparatus;of.=my;invention: ..;;(-1)..An oblong, im-section; steamwbody whose flatsides carryv undulatory' fins; .while the sides oi the. steam-containing body are fiat ;as. shown in the drawings,,.yet they 'could be madeundulatory so long as they preserved the hereinafter mentioned-principle .ot: undetached undulatory flowl" 62); .The width ofithezfinszis constant and the edge of each fin .is parallel :toa thehfiat face "of b0dc.-.,- ..1:. I -"-1 Mini) final:

J (3) The fins are .undul'atoryout of ahorizontal plane-but are not undulatory out of .a vertical plane'and, therefore, there is no. marked lateral change indirection of the air stream by reason of either the. fins or of the body of the radiator.

'.:';(4 );'I1he. fins. completely encircle the entire radiator .body both on the sides and on the. ends thereby" assisting in the entering of the air and the exit of the air and at the same time improying the. radiating qualities of the structure.

3K5.) Such an arrangement. provides a reliefv of tionecl. .as to .constitute substantially the total width of theibody. l

(fiamThe undulations of the fins. are sufiic'ient to bring about a'wiping action of theair 'on the flat surface of the body to reduce the air film on thesurface of the body to increase'heat transfer but such undulatory arrangement .is not sufficient to set up turbulence. or resistance to air. fiow so. that the air movement will be sufficiently rapid to. carry away the heat for maximum efficiency. The foregoing statement must readzin the light of the understanding of the pr'inciple' of undetached undulatory flow hereinafter explained. The'fiuid stream undu latestdapoint approaching but never attainingodetached flow. 1

8i; The undulations of' -the rib or fin in this section in this instance have a depth. only of one-thirteenth of the distance between the crowns 1ofnthe-undulations. iThe undulations must-be or" such acharacter as to preserve the principle of this invention of .undetached undulatoryifiow, whichisa new feature of the invention and 'from which results I the efiiciency secured.

' F9) The end ribs are heavy, wedge-shaped terminaLribs forreinforcing purposes.

I (10) The wall thickness is substantially twice as thich'as the rib thickness while the rib or fin surfaces are twice as great asthe bodyasur, face between the ribs so that'the thinner ribs for heat transmission present twice as greater heat radiating surface.

(11) The ribs are progressively thinner the furtherthey are from the heat source so that there will be uniform distribution of heat throughout .the rib.

(12) Theribs are spaced on adjacent bodies from one another by a distance approximately the same as the combined width of. adjacent ribs in order to provide a suflicient body ofmoving air to permit a velocity while securing maximum heat transfer. It is not intended, however," to limit the probable application to "this rabid-um I (13) The straight side walls of-the bodygive a tree sweep for the transverse steam how to reduce the internal film on the interior of the body of theradiator, thus increasing the efii ciency of the heat transfer. I I

' (14) The undulation of the fins without change of direction of the air body moving tween them is sufiicient to disturb the air film onthe outside of the body without back pres:

sure and without detachment so thatthe unde tached undulatory fiow is secured.

.(15) The air flow between the fins is of. such a nature that it is continuouswith ,anaundeta'ched 'contact'with all surfaces of: the metal boundary. The surface must not bedeprived of the close and intimate contact with thefluid in orderto prevent the loss in efficiency in the transfer of convection heat. The formation and subsequent detachment of large eddies of air due. to turbulence without intimate contact resuits: in the expenditure of energy without ade-- quate heat transfer. The present invention has the minimum area of boundary wall with the greatest transfer of heat with the least energy expenditure. This is due to the fact that the fluidstream is caused by the fins to undulate :to. a point approaching but never attaining detached flow. The eddies are correspondingly reduced in size and the speed thereof accelerated. This secures intimate contact at increased velocities with the continual change of thefluid pariticles from the center of the air stream to the tbou'ndar'y. Due to the alternate increased and decreased velocity in pressures, the air particles that are heated are continually supplanted by the cooler inner stream particles. So long asathe' angularity is sufficiently minor, the energy expenditure necessary to. produce the undulations, which energy'expenditure is proportionalto the angular change in direction added to the increased frictional resistance dueto the velocity increase-will be suflicientlysmall as to be of no importance. The slightly. increased demand for energy due to the undulations has no consequence in view of the greatly improved rate of heat transfer produced by the nudetached undulatory flow secured by this construction. Vi

iAnd, furthermore, the foregoing indicates that my invention and its physical features take into account these important propositions:

I (I) The elimination of back pressure and the increase. of velocity by using a gentle undulatory flowof the air through channels of metal havingsubstantially equal area on three sides and substantially 'equal heat distribution throughout the surface of the metal} (2) The movement of the air through such channels as to break up any air film on the surface of the metal without setting up undue turbulence and backpressure.

(3) The use of straight walls. (or undulatory walls without detachment) of a main body so that the maximum velocity of the gas, water or steam .wipes the film away on the interior of the wall decreasing its thickness and increasing heat transfer; by having the straight body the film on the interior and the exterior of the wall is reduced by the velocity ofrthe steam and the velocity of the air. 1 r

(4) The essence of this invention is the discovery of the principle referred to herein as that of f undetached undulatory flow. that the fluid stream undulates to a point approaching, but never attaining, detached flow.

Heat transfer is in proportion to the reduction in size of the eddies, in diameter and the, acceleration of those eddies'tosecure a more intimate contact and an increased velocity with the cooler air near the center of the stream and a continuoussubstitution of the fluid particles from the center of the stream to the boundary.

As a basis for a full understanding of the principles of -my method of heat transfer and a typical-construction by which m'ymethod may be practiced, the following premises should 'be understood as the basis for the practice ofmy invention. i a

This means As mypu'rpose is w'ecect a heattransferfroni the fluid having a relatively high speciflciheat, such as a prime fluid comprising steam through containing boundaries, such as cast mawoa fluid having a relatively low specific heat, such it as the secondary fluid air, it-will be understood that the prime fluid requires more contact area than the secondary" fluid. Therefore, I project from the boundaries of the radiator body on the outside where the air is flowing 'gently undulatory surfaces of such undulation as to effect the practice of this invention. If the fins 'are made zigzag, in which various parts of the fins'are at an abrupt angle to one another, then the object of the invention is completely destroyed. If the having a higher specific heat than the contained gaseous fluid in the case of'steam. a

The secondary fluid, such as air, on the outside of fthebodyisconflned by the prime surfaceand the two projecting adjacent undulatory" flns are fixed to. the prime'sur'face and conduct heat therefrom. Theseflns are so-designed asto pro vide a comparatively even flow of heat' to the boundaries of'the secondaryfluidand the spacing is such thatthe maximum heat, both of convection'and radiation, is imparted with the minimum surface friction resistance to fluid-flow. The parallel fins are .given aslight undulatory effect in direction of the fluid flow-and are car ried completely around the ends of the radiator b0dy i :i x

The relation of the angularity atany-point of these undulations must be such as to conform to the principles of turbulent-flow that I observe and such undulations must be such that, at all points on.them,there will be uninterrupted surface contact between the-air and the castiron surface. 'i

The importance ofthis arrangement can best be understood by contrast that is, straight, (Figl 8)" the fluid fiow'will have a velocity higher than the average at apoint midway between the flns with agradual-de'crease as thefln is approached.

down stream with the fluid flowbutat much lower velocity than the true stream, thus retarde ing the heat transfer'which is governed bylafunction of velocity at the point of contact Poi approximately the one half power. These eddies further retard heat transfer in that they act 'as an insulating media between the surface and "the fluid, and prevent the displacement of the film inv contact with thesurface by fluid in the m'ain stream, the removal of this eddy film from 'sur face contact and the replacement-of -eddying fluid with lesshighlyheated fluid from the main stream; and the increase with the 'prior a'rt. In the case of parallelflns', without undulations,

The friction of the 'flnsurface on the fluid will cause minute swirls. or eddies to form. These eddies revolving'on inde", pendent axes will be detached "and 'progre'ssed' Patented Jan. 15 1935 orrics -1,988,'22f4 i RADIATOR Otto G. Wendel, Buffalo,

ass idih American Radiator & standard Sanitarymgr Company, New York, N.

Delaware YQ, "a cbi iici-ation of Application February 12, 19s 4, Serial Not-7109741 :21 claims} (c1; 2'514151) My invention relates to a construction of radiator. i Y l The purpose of my invention' is to providean apparatus to practice heatjtra nsfer' from a fluid 7 havinga relatively highspecific heat,'=k:nown as a prime fluid; through containing boundaries, such as cast iron, toa fluid having 'a relatively low specific heat, dencr'ninated as'a secondary fluid.

It is the object of my invention to provide a radiator capable of being-made in sections and used as an individual sectionorin multiple sections, the characteristics of which radiator will besuperior to the radiatorsncw known in the art by reduction in weight; by the occu ancy of less space and by performing the same-heat transfer work equal to or in greater degree than the radiators of the prior art while,at the same time, provide astronger construction in order'to stand higher internal pressures than at present possiblein the art with existing radiators;

It is a further object to provide a radiator which offers materially less friction to the passage of 'air over the radiator by reducing the resistance to the passage of air while; at the same time, increasing the heattransfer.

7 It is a further object to provide a radiator, whether compared on the basis of equal friction orequal velocity, which will produce the foregoing superior features.

I have been successful in solving the 'probism of reducing the weight; the amount of space occupied and thefriction; and of increasing the rate of heat transfer fby the radiator of my invention, which is particularly useful in connectienwith heat transfer systems where an is blows over the radiaters. M-y 'i r'ivention makes possiblehigh efficiencies, as-herinafter pointed out; while, at the sametime, not "changing the material,- cast iron being employe Specifically, the foregoing advantageous results over the prior art have been secured by causing the fluidstream, such-as aim-to undulate to "a point approaching, but never attaining; detached flow, so'that, at the upstream point of new deflection, the pressure and velocity are materially increased while the eddies'are cor'isequently reduced in diameter and acceleration, thus permitting more intimate contact at an increased velocity with themore nearly virgin air near the center of the stream anda continual creased-and decreased velccift-ies and pressures,

removal or the and particles fr'bm the tester of the stream to the boundary. There 1 consequent re'ducti'on 'of vel'bcity on the stream cavity but, as this decreased velo'c-i immediately followed by an morals-eater on the same boundary surface by the n dulation, the diametersbfthe eddies a1" ventedfrom increasing to that siieheret'of; awash-net "e encountered in non-undulat element be'tween-the alternating high v high pressure and low velocity-low pressure u is insufficient to admit 6f r'fo'imat bn of an eddy diameter eneountereain abn-uiiauia "g saw; I

mi-my invention, due tothe aler at the heated boundary same-lee cf the senate continually beingreplaced by coolerinner stream-particles, thus piediiciiig a gr'atl" ii creased heating effect on the entire body of the flliid arid plbdlicifigtransfer from the pnmetothe 's'ecen "sum; requiring the minimum space; aiidji'equirmgi material in the containing bdlindaiisg I' he ener expenditure riecessar t" such unauiatiohs ispropoitiofi'ai to the angular change indirection added to the increased thetional resistance due to the velocity i'ncr The loss diie to angiilarity is sufficiently small as to benegligible; A greatly increased 'ra tepf heat transfer is, therefere; pfeducd by-und tached undulatory new at an expenditure of a negligible increasein energy.- as secure the re'regeifig-resum in my maimed of heat transfer; I arcade 3'; steam-contain i may w ose-caes um gej 1y unsanitary; fins which pre erably compietely-encir'cm, the Ste in containing body: The body itself is wager i M a plane at right angles to the directidn of means than in the direction 01 the rin and the enumerating or cooling fluid or gas is" as ranged at right anglesto the directiofifofthe fiuid or gas passing overtfie cut-side of the body guided by -the undulatory- The-undulations of the this or ribs must beef as w preserve the principle of'thi-s invention or; u'rideta'chedundulator y flowi p a This rovides a sufficim was; (if ew with the rsis tahe th 7 t6 to adequate velocity while s iiiiirgm, transfer;

a t a easy 5 willmaterially afiectfthe growth, size and velocity or the eddies interposed between the main fluid stream and the boundary surface.

1 Turningto the other customary construction in the'art of .fins having a series of portions at sharp'iFig. 9) angles to one another or having fins" that are sharply undulatory giving marked changes in direction, then the angle of undulation will be increased materially and the air flow will be changed in direction a number of times during the passage between the fins. The fluid flow, will be deflected sharply with an expenditure of. energy relative to the acuteness of angularity of the air path. The main stream will become detached from the boundary forming a low pressure area on the down stream, acute angle region between the stream and the boundary and. a swirl or large eddy will be formed having a diameter approaching the maximumwdistancebetween the parallel of the fluid stream and the maximum depth of the boundary therefrom. J The surface will be thus deprived of intimate contact with: the; fluid losing its value in theitransfer of conveoted heat,; thus materially T. reducing-its effectiveness I -The vformationand subsequent detachment of these larger eddies impose greatly increased turbulence withoutrintimate contact with a consequent increase of energy expended in producing flow betweenthese two extremes, i. e., parallel stmig-httflow, and alternate detached surface fiow v which hascha-racterized the prior art; I have found that there is a principle of construction which, when practiced, will produce the i greatest transfer of heat for the least energy expenditure with the minimum area of boundary wall: permitting a marked decreasein the weight of, cast iron employed, a decrease; in size, a reduetion in resistance to airflow and without adecrease in velocity.

The principle I have embodied,, in. my invention, in my constructionand'method of operation is to so' arrange in undulations of the fins as" toseeure a continuous undetached contact with. all surfaces of the boundary WhiGh'i call undetachedundulatory flow (Figsx'lto,8 and 'To'the'foregoing as a feature of my; invention, I have added means for entry and exit of the air so as to minimize the losses due to changes in. velocity and to maintain fluid contact with both-entry and parallel walls. At the point of entry, the vena contract, which occurs withna sharp-cornered wall, is entirely avoided By the practice of the invention embodying my principles and methods, it is possible to use undulations vertically with'respect to the stream line but alsoihorizontal with respect to the main line of the stream.

Reterring. to Figure 8, it will be seen that it shows a diagram: illustrating-the use of parallel wallxfi'ns, the walls beingv designated .13. The cone of entering air is designated 14' and two relatively thickcstreams. of turbulent eddies 15 serve to insulate the body 14- of airfromxthe hot walls 13-. thereby cutting. down heat transfer.

This parallel flow type is ineflicient 'for the reasons heretofore. pointed out.'- a v Turning to the other form characteristic of the prior art, (Fig. '9) which either: consists of sharpiundulations as shown, or angular undulationsit will be noted that the cone of air has an even narrower 'or thinner cone 'of air designated 16. ,Thiscone of air only touches at intervals at 1'7 the sharply bentwalls 18 while the spaces illustrates the detached therebetween in the deep valleys 19 areflfilled with very large areas of turbulent'air, 20;

acteristic' of the other class of the prior art which is unsuccessful for heat transfer. W

Turning' to Figure 10, which illustrates the, present invention, it ,will be :notedthat the body; of air 21 passing between the 7 engages; over a relatively long area indicated at 22 the adjacent areas onthesurfaces of thefins Land whatever small eddies are set up asat23- are-:of very minor character movement of the hot air which is quickly heated dueto the diameter, of the eddies 23 being small and due to, the fact that these eddiesmove easily into portions of the body of thecooler air 21-. and exchange plaees with other small eddies of.

cold air, thereby efiecting a rapidheat transfen,

It will be further apparent upon studying these diagrams, which illustratev graphically the practical tests and laboratory research results, that I have secured, that the body of air passing through in Figure 10 is much larger than in Figtires 8 and 9. Furthermore, the areapf contact of the-body 2 1 of air in Figure 10 is much greater than inFigures 8 and 9. It will beobserved that the (169 p areas of turbulence ,in Figures 8; and 9 which act as insulation areas between the heated fins and the body of cold air l,4=-:-or =1 6,.

are absent in- Figure 10 of the present invention.

e e U desire to comprea hend within my invention such modifications as maybe necessary to adapt ittovarying .conditions and uses).

Having thus fully use 11 in combination, a heating .body arranged for "l'ieating fluid to flow therein over unimpeded surfaces, a plurality of parallel undulating fins arranged on the exteriorof the bodyfor guiding air thereover, said undulationsbein'gsufficient to cause the air to undulate to a point approaching but heated surfaces of the body and fins, andmeans comprising continuations of the fins at the entry and. exit from the space therebetweenfor; guide ing' the air into and from between the finswith out turbulence. I b 9 2 In a rad ator, a body forminga heating chamber having oppositely-disposed inlet. a and outlet openings, said body being rectangular in cross section, and aplurality of. undulatory fins mounted on the side walls thereof, the undulations of said fins having. a maximum ,deflectign of approximately ,one-twenty-seventh of the'disundulatory flow char;

never attainingdetached flow over "the but are suflicient to cause I stance betweencenters of the undulations below and above a center line of the fins measured with respect to the distance between the nfi adjacent undulations. Y v

3. In a radiator, a body forming.

chamber having oppositely-disposed inlet and outlet openings, said body being rectangular cross section, and a plurality of. undulatory fins mounted on -the -side walls thereof, theundula tions of said fins having a vertical deflection of approximately 11/64ths to 13/64ths of an inch above and below a center line of the fins'me'as-- ured with respect to the distance between the centers of adjacent undulations, and the space between adjacent fins being an approximate average width of one-half inch. M

p 4. In a radiator, a body forming a heating chamber having oppositely-disposed inlet and outlet openings, said body being rectangular in cross section, and a plurality of undulatory fins mounted on the side walls thereof, the undulations of said fins having'a vertical deflection of approximately 11/64ths to 13/64ths of an inch above and below a center line of the fins measured with respect to the distance between the centers of adjacent'undulations, and the space between adjacent fins being an approximate average width of one-half inch, and the depth between said fins being slightly greater than one-half inch. 1

5; In a radiator, a body forming a heating chamber having oppositely disposed inlet and outlet openings, said body being rectangular in cross' section, and a plurality of undulatory fins mounted on the side walls thereof, the undulations of said fins havinga vertical deflection of approximately l1/64ths to 13/64ths of an inch above and below a center line of the fins measured with-respect to the distance between the centers of adjacent undulations, and the space between adjacent fins being an approximate average width of one half inch, and thefdepth between said fins being slightly greater than one-half inch, said fins being wedge-shaped with the base of the wedge on the heating body.

--6. In a radiator, aibody'forming a chamberhaving oppositely-disp inlet and outlet openings, said "body being rectangular ;in cross section, and a plurality 01f encircling undulatory fins,*said fi ns being heavier across, the endsoi the body than on--the sides. 7. In a radiator, afbod'y formingiachamber having oppositely-disposed inlet and outlet openings, said body being rectangular in cross section, a plurality of encircling undulatoryfins, said fins being heavier across the lends of the body than on the sides, 'and wedge-s haped throughout theirlength.

8 In a radiator, a body forming a chamber having oppositely-disposed inlet and outlet openings, said body being rectangular in cross section, a plurality of encircling undulatory fins, said fins being heavier across'the ends of the body than on the sides, and wedge-shaped throughout their length, the ends of said body and the ends of said fins tapering to, an edge forming a ridge on the ends of the body. 1

9. In a radiator, a body forming a chamber having oppositely-disposed inlet and outlet openings, said body having flat side .walls and a plurality of encircling undulatory fins, each of said fins extending entirely around said body.

10, In a radiator, a body forming a chamber having oppositely-disposed inlet and outlet openings, said body beingrectangular in cross section with fiat side walls 'and a plurality of encircling undulatory fins, .each of said fins extending entirely around said bodyand said fins having their outer margins parallel to the surface of the side walls of the radiator I 11. In a radiator, a body forming a chamber having oppositely-disposed inlet and outlet openings, said body being rectangular in cross section with fiat side wallsiand a pluralityiof encircling undulatory fins, each of said fins ex tending entirely around said body and said fins encircling undulatory fins, said fins having their outer margins parallel to thesurface of? the side walls of the radiatorbody and spaced fromone another a distance equal to approximately the height of'one of them whereby a channel is formed for the'passage of air substantially form cross section between the metal walls defining the channel, and said radiator body wall and fins being ofsubstantially equal thickness;

13. In a radiator, a body forming a chamber having oppositely-disposed inlet and outlet openings, said body being rectangular in cross section with fiat side walls and a plurality- -'oi" encircling undulatory fins, said fins having thelr' outer margins parallel to the surface of the side' walls of the radiator body and spaced from one another a distance equal to approximatelythe height of one of them whereby a channelis formed forthe passage of air oi' substantially umform cross section between the metal 'walls defining the channel, said radiator body wall and fins being of substantially equal" thickness, the'outer portions of the fins tapering so that the lesser the'heat the lesser'the metal to insure uniform heat distribution to the air in the passageway formed by the radiator body wall and undulatory fins. Y I

14. In 'combination, means forforming-a, passageway, a plurality of parallel interconnected radiator sections arranged transversely of the passageway, and a plurality of similar sections arranged behind 1 in staggered relationship With respect to the preceding sections, and a plural ity-of undulatory-fins mounted on each of said sections,'thefins of each section being disposed opposite to the fins of the adjacent 'sectionin spaced relationship thereto, and means oiiorc ing a blast of air over said sections and between m' 15. In combination, means for forming apassageway, a plurality of parallel interconnected radiator sections arranged transversely 'of the passageway, a plurality'of similar "sections arranged behind in staggered relationship with respect to the preceding sections, and a plural ity of undulatory fins mounted oneach or said sections, the fins'of each section beingv disposed opposite to the fins of the adjacent section in spaced relationship thereto, 'andmeans of forcing a blast of air over said'sectionsand between them, said fins beingso arranged as to provide an undulatory movementfor the air approaching but never attaining detached flow over. the heated surfaces of the radiator'sections. i

.16. In'a radiator,.a body forming aheating chamber and a plurality of spaced ribs" on the sides thereof inclined from one end of the :rib to the other, said ribs being undulatory, said undulations varying from the center axis of the undulatory rib from 11 /64ths to 13/64thsfoi. an incht v 1'7. In a radiator, a body forming a heating chamber and a plurality of spaced ribs on the sides thereof inclined from one end of the rib to the other, said ribs being undulatory and completely encircling the heating body.

18. In combination, a heating body arranged for heating fiuid to flow therein, a plurality of parallel undulating fins arranged on the exterior of the body for guiding the air thereover, said fins extending beyond the ends of the heating body, each fin continuously encircling said body.

19. In combination, a heating body arranged for heating fluid to flow therein, a plurality of parallel undulating fins arranged on the exterior of the body for guiding air thereover, said fins extending beyond the ends of the heating body, each of said fins entirely encircling said body and the undulation of said fins being sufficient to cause the air to undulate to a point approaching but never attaining detached flow over the heating surfaces of the body and fins.

20. In combination, a heating body arranged for heating fluid to flow therein, a plurality of parallel undulating fins having crests and troughs arranged on the exterior of the body for guiding the air thereover, the troughs of said undulations extending below the crest to an extent between 11/64ths and 13/64ths of an inch from a horizontal line to which the crests of the undulations are tangent.

21. In combination, a heating body arranged for heating a fluid to fiow therein, a plurality of parallel undulating fins arranged on the exterior of the body having crests and troughs for guiding the air thereover, the troughs of said undulations extending below the crest to an extent between ll/Giths and 13/64ths of an inch from a horizontal line to which the crests of the undulations are tangent, said undulations being sufficient tocause the air to undulate to a point approaching but never attaining detached fiow over the heated surfaces of the body 20 and fins.

, OTTO G. WENDEL. 

